We describe a case of fever of unknown origin (FUO) of 9 months' duration in which the finding of regularly spaced multiple Beau's lines (the "ladder nail" sign) pointed to the possibility of a relapsing fever of the Pel-Ebstein variety and an underlying lymphoma. Subsequent investigation confirmed the association of the Beau's lines and fever, as well as the diagnosis of Hodgkin's disease as the cause of the FUO. In this setting, Beau's lines may provide an important diagnostic clue and should be carefully looked for on physical examination.